1. Field of the Invention
The present invention relates to an imaging apparatus such a CDD, a video camera, or other camera that makes use of solid-state imaging elements.
2. Description of the Related Art
In current video cameras, a solid-state imaging section (CCD image sensor) that is formed by a plurality of solid-state imaging elements, is used as an imaging means that is smaller and lighter than an imaging tube and which can be produced at a low cost. The construction of a general type of CCD image sensor is shown in FIG. 1.
FIG. 1 shows a CCD image sensor 50 that has a plurality of photoelectric conversion elements 51, which are formed by a plurality of elements that receive light of differing color and store this light as electrical charges, these being arranged in the vertical direction, a plurality of vertical transmission paths 52, which transmit the electrical charges that are stored by the photoelectrical conversion elements 51 in the vertical direction, and a horizontal transmission path 53, which transmits a charge in the horizontal direction that is transmitted by the plurality of vertical transmission paths 52.
In a CCD image sensor 50 such as noted above, the photoelectric conversion elements 51 and the vertical transmission paths 52 are arranged in alternating manner in two dimensions, the electrical charge that is stored by each photoelectric conversion element 51 being output via the vertical transmission paths 52 and the horizontal transmission path 53 each field period.
In the above-noted type of CCD image sensor 50, however, in order to improve the dynamic image resolution, a high-speed imaging method has been developed, whereby the electrical charge that is stored by each of the photoelectric conversion elements 51 is read out a plurality of times during a given field period, thereby forming a plurality of screen images.
However, to achieve high-speed signal imaging in a CCD image sensor having the above-noted configuration, there was an accompanying problem of the need to make the transmission frequency of the vertical transmission paths 52 and the horizontal transmission paths 53 high.
Specifically, to form a plurality of screen image with the field period not extended, but rather left as the same length as in the past, it is necessary to make a commensurate increase in the transmission speed and the signal processing speed. As a result, a decrease in the efficiency of transmission, and the difficulty of achieving correlated double sampling (CDS) and automatic gain control (AGC) at high frequency lead to a deterioration of the signal processing, and another means must be provided to avoid this problem.
The present invention was made in consideration of the above-noted problems with the related art, and has as an object the provision of an imaging apparatus that achieves high-speed imaging, without a major change to an imaging device of the past, such as a CCD.
To achieve the above-noted object, there is provided an imaging apparatus that has: a solid-state imaging section, which is formed by a plurality of photoelectric conversion element, which convert input light to an electrical charge, these photoelectric conversion elements being disposed in a matrix arrangement, and a controller, which performs control so as to read out the electrical charge that is stored in the photoelectric conversion elements over a prescribed area of the above-noted plurality of photoelectric conversion elements a plurality of times during one field period.
A preferred embodiment of the present invention further has a drain section, which drains off, at one time, the electrical charges that have been stored by a series of photoelectric conversion elements arranged in the horizontal direction, wherein the controller performs control so that the electrical charges that are stored by photoelectric conversion elements other than the photoelectric conversion elements of the prescribed area are all drained off at one time by the drain section, so that the electrical charges that are stored by the photoelectric conversion elements of the prescribed area are read out a plurality of times during one field period.
In an imaging apparatus according to the present invention as noted above, with regard to the prescribe area (to be referred to as the normal transmission area with regard to the embodiments to be described), the electrical charges that are stored by the photoelectric conversion elements are read out in a manner similar to the case of an imaging apparatus of the past, processing being passed on and an image being formed without draining off these charges. On the other hand, with regard to area (to be referred to as the high-speed transmission area with regard to the embodiments to be described) other than the prescribed area, the electrical charges that are stored by the photoelectric conversion elements are drained off or are not read out thereby increasing the processing speed. As a result, according to an imaging apparatus of the present invention, it is possible to achieve an improvement in dynamic image resolution of the acquired image, without extending the overall image processing time.
In a preferred embodiment of the present invention, each of the plurality of photoelectric conversion elements detects one of a plurality of prescribed colors, these plurality of photoelectric conversion elements being driven by a plurality of fixed patterns repeatedly in the vertical direction, the above-noted prescribed area being defined by units of the above-noted fixed pattern.
In the present invention, because the normal transmission area starts with the first photoelectric conversion element within one fixed pattern, there is no change in the imaging signal pattern that accompanies a change in the size of the normal transmission area, so that continuous image processing is possible even after a change in the size of the normal transmission area.
In a preferred embodiment of the present invention, the solid-state imaging section includes a photoelectric conversion element that is optically blocked, for the purpose of detecting a vertical black reference, the readout controller performing control so that each time an electrical charge that is stored by a photoelectric conversion element in the prescribed area, the charge stored in the photoelectric conversion element for the purpose of detecting the vertical black reference is read out.
In this manner, during one field period, by performing readout of the electrical charge a plurality of times, and also by reading the optical black reference (referred to hereinafter as VOB) a plurality of times during one field period, it is possible to accurately adjust the black reference for each image. In this case, when reading out an electrical charge a plurality of times during one field period, if the VOB is read out before the electrical charge is read out, it is possible to use this VOB data in, for example, smear detection.